1. Field of the Invention
The present invention relates to a method for manufacturing a coil formed of a conductor of rectangular cross section and used in an electric apparatus such as a motor or a transformer.
2. Description of the Related Art
Conventionally, a conductor of rectangular cross section is wound as it is to obtain a coil.
This method involves the formation of a projection, such as a thick-walled portion or a deformed portion, at the inner side of a coiled conductor. Since such a projection may cause dielectric breakdown or a like failure, the projection is made smooth by use of a coil surface leveler as disclosed in, for example, Japanese Patent Application Laid-Open (kokai) No. 57 (1982)-68222.
However, the conventional method for manufacturing a coil involves the following drawbacks.
First, since a separate surface leveler is required, the number of manufacturing apparatuses and the number of production steps increases, with the result that the cost of manufacture increases, and productivity decreases.
Second, projections projecting in the axial direction of a coil can be eliminated, but other projections projecting toward the center of the coil may be newly generated, and deformed portions cannot be completely eliminated, thus resulting in failure to obtain a coil of high quality and excellent homogeneity.